Field of the Invention
This invention relates to an edge roll assembly employed for rolling a sheet spring material in its breadth direction in a taper leaf manufacturing apparatus by which after the edges of a sheet spring material are rolled in its breadth direction, the material is subjected to rolling in its thickness direction.
A taper leaf employed for the construction of a laminated spring is such a leaf that tapers are formed at both ends of a flat sheet.
The conventional method for manufacturing such a taper leaf is to form tapers by performing rolling work in varying press-down amounts by means of two rolling rolls or one rolling roll while transmitting a spring material. At this time, naturally, expansion towards sidewise direction takes place at the worked terminal of a sheet spring material, accompanying rolling work. If breadth enlarges due to sidewise expansion, there appear problems in regard to quality such as stress distribution and weight lightening and problems in regard to manufacturing such as fabrication. Therefore, it is necessary that the portion having expanded breadth should be adjusted by means of cutting, grinding and abrading, press work, etc. before or after taper rolling. That is, work is to be carried out by pre-estimating breadth expansion due to rolling, amending beforehand the amount of breadth by means of a cutter blade, a breadth narrowing press, etc. and then taper rolling or by applying the above amending process after taper rolling. However, there are defects that these operations have little prospects of success and the shapes of both sides of a leaf spring are poor at the time of completion, or especially in case of breadth narrowing press, a warp is caused in sidewise direction at a sheet spring material so that buckling is brought about.
Except the above process, there is a process that by making small the diameter of a rolling roll so as to make little the rolling amount at one time, the amount of breadth expansion is made less and rolling is repeated a number of times. However, in this process, rolling efficiency is bad and breadth expansion cannot be fully suppressed. Furthermore, there is a taper rolling method in which metal molds, grooved rolls, etc. are employed so that sidewise expansion is suppressed at a worked sheet spring material. In this method, the emergences of swells and scars are feared and the quality maintenance is difficult.